I put a Factory Mach 1000 stereo from a 2002 Mustang stereo in my 2000 Mustang but I retained the original radio/CD player. A problem I ran across is the power-on signal coming from the radio is 4.4 volts with the original 3 amps plugged in and the new Mach 1000 amps require 7 volts to turn them on. It seems like I need a relay that would turn on with the 4 volts coming from the radio power-on signal and a resistor to drop the 12 volts from the battery to 7 volts to turn on the new amps. An alternative would be to use a 7 volt power supply that could be turned on by the 4 volt radio power-on signal. My question is, which one of these approaches would be better and where can I find a relay that would turn on with 4 volts?

 

any radio shop should have the module i thing is about $45.00